GE CareScape V100, Service Manual

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B-2 CARESCAPE V100 Vital Signs Monitor 2048723-002C
Appropriate use of NIBP simulators: Appropriate use of NIBP simulators
Appropriate use of NIBP simulators
NIBP accuracy
Noninvasive Blood Pressure (NIBP) monitors are cleared for sale in the U.S. by the
FDA (1) and in Europe through the CE Mark. Both of these processes require that
the accuracy of NIBP monitors be established through clinical testing - the use of
NIBP simulators is not acceptable.
GE Healthcare has established accuracy using the AAMI SP-10 standard (2) and
a similar standard exists in Europe (3). The AAMI standard specifies that the
accuracy of NIBP monitors can be determined using either an invasive (intra-
arterial) or noninvasive (auscultatory) blood pressure reference. Over the last 30
years, DINAMAP
®
accuracy has been established using an invasive central
aortic blood pressure reference. More recently, the CARESCAPE V100 vital signs
monitor has also been validated against a manual auscultatory reference.
Clinical vs. simulator readings
There are a number of reasons why the clinical studies are required for the
measurement of NIBP accuracy. Many physiologic measurements (e.g., ECG, HR,
eTCO2) can be taken with little interaction between the monitor and the patient.
These devices can typically be validated using previously recorded patient data.
Unlike the transducers/electrodes used in these devices, the NIBP cuff has two
functions. In addition to sensing the pressure pulses in the cuff, the cuff occludes
and then releases the patient's artery to create the conditions that allow blood
pressure to be measured.
An "artificial arm" would need to test both the sensing and occluding functions of
the cuff, and mimic the nonlinear dynamics of the artery to provide an effective
clinical simulation. While this has been attempted (4), there are no effective
"arms" available.
Commercial NIBP simulators do attempt to test both functions of the NIBP cuff.
Pressure signals are generated by the simulator in response to the inflation and
deflation cycles of the monitor. While the cuff may be in the system, it is
wrapped on a mandrel. The ability of the cuff to transducer pressure signals or
to occlude the artery is not tested.
There are further limitations to the pressure pulses used by simulators. During
the deflation of the cuff, the shape of the generated pressure oscillations
changes as the cuff goes from systolic to diastolic pressures. This is due to the
fact that the artery is only open when the arterial pressure is above cuff
pressure. As can be seen in Figures 1A-1C, the shape of the oscillation changes
as the cuff pressure changes, and the artery opens. Commercial NIBP simulators
use one waveform shape at all pressure levels, which is simply scaled to reflect
the oscillometric envelope.
In addition, the shape of the oscillation generated by commercial simulators
does not match the shape of a typical oscillation measured during clinical
testing (Figures 2A-2B). These differences in the shape of the pulses can effect